Disc brake rotor thickness wear and score depth gauge and method of using same

ABSTRACT

A gauge is provided with a plate for positioning the gauge against one surface of a part to be measured, and a biased pointer for engaging the opposite surface of the part. Means are provided for permitting the pointer to be moved perpendicularly with respect to the plate. One edge of the pointer is a gear which meshes with a gear to drive an indicator which amplifies the gauge reading on an arcuate scale. A second indicator can be moved independently to a plurality of fixed positions on the scale.

United States Patent McFarland et a1.

[54] DISC BRAKE ROTOR THICKNESS WEAR AND SCORE DEPTH GAUGE AND METHOD OFUSING SAME [72] Inventors: Frederick R. McFarland; Walter L.

Diftenderfer, both of Lancaster, Pa.

[73] Assignee: K-D Manufacturing Company, Lancaster, Pa.

221 Filed: March 22,1971 211 App1.No.:101,154

Related US. Application Data [63] Continuation of Ser. No. 830,029, June3,

1969, abandoned.

[52] US. Cl ..33/147 F [51] Int. Cl. ..G0lb 5/00 [58] Field ofSearch..33/l47 A, 147 J, 147 H, 147 M [5 6] References Cited UNITEDSTATES PATENTS 744,796 11/1903 Reilly ..33/147 [451 Sept. 19, 19722,134,262 10/1938 Phillips ..33/148 904,560 11/1908 Pierpont ..33/l471,358,794 11/1920 Stewart.. ..33/147 836,605 11/1906 Provandie ..33/147FOREIGN PATENTS OR APPLICATIONS 157,628 1/1921 England ..33/147 PrimaryExaminer-Leonard Forman Assistant Examiner-A. J, Mirabito Attorney-Paul& Paul [5 7] ABSTRACT A gauge is provided with a plate for positioningthe gauge against one surface of a part to be measured, and a biasedpointer for engaging the opposite surface of the part. Means areprovide-d for permitting the pointer to be moved perpendicularly withrespect to the plate. One edge of the pointer is a gear which mesheswith a gear to drive an indicator which amplifies the gauge reading onan arcuate scale. A second indicator can be moved independently to aplurality of fixed positions on the scale.

4 Claims, 3 Drawing; Figures PATENTEDsEPIQ m2 3.691.640

sum 2 or 2 v INVIENTORS FREDERICK R. Mc FAIRLAND 8\ WALTER .L.DIFFENDERFER PAUL a PAl JL ATTORNEYS DISC BRAKE ROTOR THICKNESS WEAR ANDSCORE DEPTH GAUGE AND METHOD OF USING SAME CROSS REFERENCE TO RELATEDAPPLICATION This application is a continuation of our prior copendingapplication for a Disc Brake Rotor Thickness Wear and Score Depth Gauge,Ser. No. 830,029, now abandoned filed, June 3, 1969 and discloses andclaims the subject matter in that application.

BACKGROUND OF THE INVENTION This invention relates to hand operatedgauges of the caliper type for measuring the thickness of parts, andmore particularly, to a manual gauge for measuring the thickness of therotor or disc in a disc brake and the depth of the score marks, if any,in the surface of the rotor.

Disc brakes used on automobiles comprise a rotor mounted to a shaftwhich turns between a pair of shoes disposed about the opposite faces ofthe disc or rotor. Fluid pressure exerts force on pistons to press thelinings of the shoes against the rotor faces. As in conventional brakes,the linings wear and the surfaces against which they are pressed wear.Just as in conventional brakes, these surfaces must be periodicallyinspected, for safety reasons, and many states are now requiring such aninspection.

It is desirable to provide a gauge which is simple to use, and which mayreadily be operated by a mechanic to give an accurate determination ofthe depth of any score lines on the rotor and of the overall wear of therotor. At the same time it is desirable to have a device which issufficiently small to be carried within the pocket of the mechanic andwhich, while giving a clear easily' readable presentation of themeasurement made, is capable of making very slight destinations andhighly accurate measurements.

SUMMARY OF THE INVENTION This invention comprises a body having a baseportion and measuring means moveable toward and away from said baseportion, said body including a scale and having mounted thereon inengagement with said measuring means indicating means for movement inresponse to movement of said measuring means to indicate distancesmeasured from said base portion on said scale. In the preferredembodiment of the invention auxiliary indicating means are providedwhich can be preset to a plurality of positions on said scale.

Accordingly, it is an object of this invention to provide a compactgauge capable of accurately indicating wear and thickness of a scoredrotor.

This and other objects of our invention will become apparent from thefollowing description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of our inventionpartially broken away for the sake of clarity and showing a brake rotorin operative position with the device; with alternate positions shown inphantom;

FIG. 2 is a section taken as indicated by the lines and arrows 2-2 inFIG. 1; and

FIG. 3 is a plan view of the other side of the device when viewed as inFIG. 1 with some of the parts shown in alternate positions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although specific forms of theinvention have been selected for illustration in the drawings, and thefollowing description is drawn in specific terms for the purpose ofdescribing these forms of the invention, this description is notintended to limit the scope of the invention which is defined in theappended claims.

Referring to the figures, the gauge shown comprises a body 10 whichincludes a flat arcuate portion having indicia forming a scale 11thereon along the arcuate edge thereof. The scale is incremented to givereadings in units of 0.010 inches from 0.300 to 1.300 inches. This scalewas designed for use with common rotors for disc brakes now being usedin the automotive industry. Of course, it is to be understood that thescale could be varied if necessary within the scope of this invention.

Fixedly attached to the body is a base 12 which is arranged to beperpendicular to the plane of the body. As shown more clearly in FIG. 2,the base extends on either side of the body to provide a flat planesurface presenting itself to the rack 14. The rack is supported alongone edge of the body by a plurality of shouldered studs 16 and 18 whichare pressed into the body 10 and the coverplate 20, and space the plateand body apart. The coverplate extends over a large portion of the bodyand its arcuate edge stops short of the scale 11 and is supported ateither end by screws .22 and 24 which pass through spacer bushings andare fastened in the body 10 so that the plate 20 is maintained in spacedrelation to the body 10.

Elongated holes 25 and 26 are provided in the rack 14 which along anaxis A perpendicular to the base plate 12. The lead end of the rack hasa beveled edge terminating in a point 28 which lies on the axis A. Thetrailing end of the rack has a handle 30 similar to that of a key. Therack is in a close sliding fit between the coverplate 20 and'the body 10and the studs 16 and 18 are in a sliding fit in their respectiveelongated slots.

Along the edge of the rack which is disposed between the coverplate andthe body, a gear 32 has been cut to run parallel to the axis A. The gearis designed to mate with the pinion 34. The pinion 34 is mounted torotate about a stud 36 which is securely fastened to the body 10 andcoverplate 20. Extending from one side of the pinion 34 is a pointer arm40 having a V-shaped point 42 at the outwardly extending end thereofdisposed to overlie the indicia on the scale 11 and to indicate thereading being made.

It will be apparent from'what has been disclosed thus far that uponmovement of the key-shaped rack 14 to the left or right the pinion 34will be swung about the stud 36 and the pointer will move along thescale.

To aid in making readings on a rotor, the pinionpointer is spring biasedto drive the rack 14 toward the base plate 12. The means for biasing thepointer comprises a coiled spring 44 disposed about the stud 36 in aspaced relation therefrom and having a hook 46 at one end engaging thepointer arm 40, while the other end 48 passes through a slot 49 in theside of the coverplate 20.

The pointer arm 40 is bent in a U-shape to accommodate the hook 46 ofthe spring, so that the spring clears the surface of the body 10. Thenormal condition of the spring 44 is compressed, so that as it tries tounwind, the pinion is rotated counterclockwise about the stud 36 (whenviewed as in FIG. 1). Since the pinion is freely rotatable in the studand the rack is readily slideable in its mountings, the effect of thisspring action is to cause the rack to move toward the base plate. Thuswhen a rotor, such as the rotor 50 in FIG. 1, is disposed between therack and the base plate, the rack would normally engage the face of therotor. The distance at which the end of the rack is positioned from thebase plate when the rack is against the face of the rotor will be shownby the pointer on the scale.

Its desirable when using this gauge to have an indication readilyvisable of what the optimum desired readings should be. In this regardwe have provided a means for manually indicating the optimum desiredreading prior totaking a measurement with a gauge. The manual indicator60 embraces the arcuate edge of the body with a inwardly directedpointer 62 and extends around the rear of the gauge with a long arm 64best illustrated in FIG. 3. The arm 64 is pivotally connected to thestud 36 which extends through the arm and the spring washer 66 and isthen rolled over. The spring washer, is in compression between therolled head of the stud and the arm 64, so that while the pointer 62 maybe readily moved by hand to any point on the scale 1 1, it will not moveof its own accord. Thus it will remain in the spot to which it is moved.The arm 64 is bent in a U-shape, so as to provide a convenient means forengaging the arm with the index finger and moving it along the scale. Y

In operation a mechanic will check the original manufacturersspecification for rotor thickness, and then preset the manual indicator62 to the original thickness position on the scale. To reiterate eachscale line equals 0.010 inches. Holding the gauge in one hand, he willthen grip the handle 30 and pull the rack away from the base plate 12.With the gauge in this position, he will slip the gauge over the discbrake rotor and hold the base plate flat against one side of the rotoras in FIG. 1. Then he will release the handle and the rack 14 willengage the other face of the rotor as shown in phantom in FIG. 1. If therotor is not worn, both the preset indicator 62 and the pointer 42 willbe at the same place.

FIG. 1 shows the gauge in its position in full lines wherein it has justbeen inserted over the rotor 50 and the base plate 12 laid flat againstit. Note that the pointer 42 is to the left of the manual indicator 62.When the rack is released and the point 28 of the rack engages the rotoras shown in phantom, the pointer will move to the manual indicatorposition 62 as long as the rotor is exactly what it should be inaccordance with the manufacturers original specifications. However, ifthe rotor is worn the pointer will move farther to the right as shown inphantom (that is, counterclockwise about the stud 36) and the differencebetween the manual indication at 62 and the phantom reading will showthe wear of the rotor.

To check the depth of scores in the rotor, the previous steps arerepeated and in addition the mechanic will move the gauge instrumentradially in and out with the plate 12 held firmly against one surface,allowing the point 28 to traverse over the other surface. The taperedpoint on the rack will go into the low spots and over the high spots,while the mechanic checks the variance on the scale. As previouslyindicated, the range of the scale if from approximately three-eighths ofan inch to approximately 1 /4 inches so as to correspond to disc rotorsused on American and foreign manufactured automobiles. To get anaccurate check on all surfaces of the rotor, the gauge can be movedcircumferentially about the axis of the rotor and different measurementscan be taken radially.

As shown in the rear view FIG. 3 and the rack 14, when inserted fully,positions the pointer 42 at one end of the scale and yet does not touchthe base plate 12. This has been compensated for by arranging the scaleand the distance which the base plate is spaced from the body 10, sothat the scale reads accurately when a rotor is positioned between therack and the base plate. Thus in the position shown the rack would bepositioned 0.300 inches from the base plate.

It will be understood that various changes in the details, materials andarrangement of parts which have been herein described and illustrated inorder to explain the nature of this invention, may be made by thoseskilled in the art within the principle and scope of the invention asexpressed in the following claims.

It will further be understood that the Abstract of the Disclosure setforth above is intended to provide a non-legal technical statement ofthe contents of the disclosure in compliance with the Rules of Practiceof the US. Patent Office, and is not intended to limit the score of theinvention .described and claimed herein.

What is claimed is:

l. A disc brake rotor thickness wear and score depth gauge, comprising:a body having one arcuate edge and a flat'plane departing from said edgehaving indicia disposed along said flat plane and terminating along saidedge; said body having a thin, flat plate extending therefromtransversely with respect to said flat plane, a portion of said thinflat plate being offset from the remainder thereof; a rack, slidablymounted on said body for movement substantially perpendicularly towardand away from the flat surface of said plate, said rack having aV-shaped pointer on one end thereof, said end being closest to saidplate, said rack having gripping means at the other end thereof, saidgripping means comprising an enlarged handle portion; a plurality ofpins fixedly mounted in said body; said rack having a plurality ofelongated slots therein, each of said slots being disposed about a pin,whereby said rack is in sliding engagement with said plurality of pins;said elongated slots being of predetermined length and retaining saidrack so that said rack moves in a perpendicular path with respect tosaid plate between predetermined limits, said limits being fixed so thatthe V-shaped pointer end of said rack is always spaced from said thinflat plate; said plate being thinner than the distance between saidplate and said V-shaped pointer; a pinion rotably mounted to said bodyand engaging said rack for movement in response to movement of said rackand having a pointer connected thereto extending therefrom overlyingsaid indicia to cooperate with said indicia for directly indicatingmeasurements corresponding to the distance between the V-shaped pointedend of said rack and the closest surface of said flat plate; saidpointer being spring biased by a spring means engaging said pointer andsaid body to urge said rack toward said plate; a cover portion overlyingsaid spring and pinion and rack and being fixedly attached to said body;said pointer extending from beneath said cover plate and being free totraverse along said indicia in response to movement of said rack; and aseparate indicator means pivotally connected to said body for movementto a plurality of fixed positions along said indicia, said separateindicating means comprising a pointer overlying said indicia andcooperating with said indicia for making predetermined fixed indicationsalong said indicia; said separate indicator means embracing said arcuateedge; said separate indicator means being frictionally engaged with saidbody whereby said pointer is held in the positions to which it is moved.

2. A method of measuring disc brake rotor thickness and score depth byuse of a gauge having a body with an arcuate scale along one flatsurface and a flat plate extending from said body transversely to saidflat surface and a rack spaced from said flat plate and retained on saidbody to move perpendicularly with respect to said thin flat plate, saidrack having a V-shaped pointed end on the end thereof closest to saidthin flat plate, said rack engaging a pinion having a pointer extendingtherefrom overlying said indicia to directly indicate in cooperationwith said indicia the distance between the end of said V-shaped end ofsaid rack and said thin flat plate; said pointer being spring biased todrive said pinion and said rack toward said thin flat plate; and anadditional manual indicator pivotally and frictionally engaging saidbody having an additional pointer at the free end thereof overlying saidindicia and being capable of being manually moved to a plurality ofpredetermined positions in which it will remain until moved again;comprising the steps of: manually inserting the thin flat plate into anassembled disc brake so that the surface of the thin flat plate closestto the pointed end of the rack engages one radially extending surface ofthe rotor of the disc brake, while simultaneously withdrawing the rackso that the pointed end clears the edge of the rotor so that the gaugecan be fully inserted about the rotor, whereby the plate and pointed endembrace the radially extending surfaces of the rotor; next moving theflat plate so that it lies flush against the radially extending surfaceof the rotor which it had previously engaged; next releasing the rack toallow the spring biasing means to force the rack against the otherradially extending surface of the :rotor; next withdrawing the gaugefrom the disc brake assembly while simultaneously observing the positionof the pointer extending from the pinion overlying the indicia toobserve the directly indicated measurements. of disc brake rotor movinthe a e ircu fere tiall about he axis f the roFor to a pl ralityoppositions viiherem t e gauge is moved radially in and out, so thatadditional measurements can be observed.

1. A disc brake rotor thickness wear and score depth gauge, comprising:a body having one arcuate edge and a flat plane departing from said edgehaving indicia disposed along said flat plane and terminating along saidedge; said body having a thin, flat plate extending therefromtransversely with respect to said flat plane, a portion of said thinflat plate being offset from the remainder thereof; a rack, slidablymounted on said body for movement substantially perpendicularly towardand away from the flat surface of said plate, said rack having aV-shaped pointer on one end thereof, said end being closest to saidplate, said rack having gripping means at the other end thereof, saidgripping means comprising an enlarged handle portion; a plurality ofpins fixedly mounted in said body; said rack having a plurality ofelongated slots therein, each of said slots being disposed about a pin,whereby said rack is in sliding engagement with said plurality of pins;said elongated slots being of predetermined length and retaining saidrack so that said rack moves in a perpendicular path with respect tosaid plate between predetermined limits, said limits being fixed so thatthe Vshaped pointer end of said rack is always spaced from said thinflat plate; said plate being thinner than the distance between saidplate and said V-shaped pointer; a pinion rotably mounted to said bodyand engaging said rack for movement in response to movement of said rackand having a pointer connected thereto extending therefrom overlyingsaid indicia to cooperate with said indicia for directly indicatingmeasurements corresponding to the distance between the V-shaped pointedend of said rack and the closest surface of said flat plate; saidpointer being spring biased by a spring means engaging said pointer andsaid body to urge said rack toward said plate; a cover portion overlyingsaid spring and pinion and rack and being fixedly attached to said body;said pointer extending from beneath said cover plate and being free totraverse along said indicia in response to movement of said rack; and aseparate indicator means pivotally connected to said body for movementto a plurality of fixed positions along said indicia, said separateindicating means comprising a pointer overlying said indicia andcooperating with said indicia for making predetermined fixed indicationsalong said indicia; said separate indicator means embracing said arcuateedge; said separate indicator means being frictionally engaged with saidbody whereby said pointer is held in the positions to which it is moved.2. A method of measuring disc brake rotor thickness and score depth byuse of a gauge having a body with an arcuate scale along one flatsurface and a flat plate extending from said body transversely to saidflat surface and a rack spaced from said flat plate and retained on saidbody to move perpendicularly with respect to said thin flat plate, saidrack having a V-shaped pointed end on the end thereof closest to saidthin flat plate, said rack engaging a pinion having a pointer extendingtherefrom overlying said indicia to directly indicate in cooperationwith said indicia the distance between the end of said V-shaped end ofsaid rack and said thin flat plate; said pointer being spring biased todrive said pinion and said rack toward said thin flat plate; and anadditional manual Indicator pivotally and frictionally engaging saidbody having an additional pointer at the free end thereof overlying saidindicia and being capable of being manually moved to a plurality ofpredetermined positions in which it will remain until moved again;comprising the steps of: manually inserting the thin flat plate into anassembled disc brake so that the surface of the thin flat plate closestto the pointed end of the rack engages one radially extending surface ofthe rotor of the disc brake, while simultaneously withdrawing the rackso that the pointed end clears the edge of the rotor so that the gaugecan be fully inserted about the rotor, whereby the plate and pointed endembrace the radially extending surfaces of the rotor; next moving theflat plate so that it lies flush against the radially extending surfaceof the rotor which it had previously engaged; next releasing the rack toallow the spring biasing means to force the rack against the otherradially extending surface of the rotor; next withdrawing the gauge fromthe disc brake assembly while simultaneously observing the position ofthe pointer extending from the pinion overlying the indicia to observethe directly indicated measurements of disc brake rotor thickness. 3.The invention of claim 2 wherein the additional step of first presettingthe manual indicator for the manufacturer'' s original thickness of aparticular disc brake rotor by moving the pointer of the additionalmanual indicator to the appropriate position overlying the indicia onthe body.
 4. The invention of claim 2 wherein the additional step ofmoving the gauge radially in and out and then moving the gaugecircumferentially about the axis of the rotor to a plurality ofpositions wherein the gauge is moved radially in and out, so thatadditional measurements can be observed.